Inconsistent Interactions with Lich’s Eternal Life

I have energy shield on my Lich with the Eternal Life ascendancy node, so my life does not change.

I am able to “sacrifice” life by using the Extraction and Ablation supports. I receive the benefit of these supports without my life total changing.

However, I cannot “spend” life to use the Lifetap support to use a skill. I receive the error message that I’m “Out of Life”.

These interactions seem inconsistent to me.